May IP addressing conflict ka. Sa switched environment, lahat ng members ay dapat may common subnetwork. Base sa diagram mo, you have 2 different subnets (192.168.1.0/24 at 192.168.2.0/24). Tapos on 2 different places, you have 2 different gateways.
In addition, what sort of networking VirtualBox has? Is it bridged or NAT?
Lastly, paki-post kung yung edge router mo (PLDT) is yung 3-in-1 (modem, router, switch) na freebie ng ISP or is it a custom gateway with 2 (or more) NICs?
In the meantime, what I can suggest is to standardized your IP addressing by deploying only a single subnet. Don't forget that you deploy different subnets only if you want them to separate at Layer 3 of OSI Model which is not applicable in your setup.
Likewise, yung DNS its either yung nasa LAN-side ng router mo; o any external DNS resolver such as 8.8.8.8 or your ISP's. Hwag yung nsa WAN-side ng router (if multi-NIC).
Short and handy mnemonic:
Layer 2 - switch. one subnet. Router is not needed for communication between clients, eg 192.168.1.1/24 and 192.168.1.10/24 can talk just fine.
Layer 3 - router. multiple, diverse subnets. Router is need for clients on different subnets to see the other, eg 10.0.0.1/24 unable to talk to 192.168.0.1/24 without the help of a router.